1. Field of the Invention
The present invention relates to a hydraulic damping device for damping vehicle oscillations such as roll, pitch, bounce, etc. and particularly to the type capable of producing a variable damping force in accordance with a kind of oscillation, i.e., whether an oscillation causes relative vertical movement between two wheels, such as roll, pitch, etc. or does not cause such relative movement, such as bounce, etc.
2. Description of the Prior Art
An example of a damping device for damping a vehicle oscillation is disclosed in Japanese Provisional Publication No. 60-76506.
This prior art device is incorporated in a suspension system and includes a pair of single rod-double acting hydraulic cylinders installed between a vehicle body and respective suspension arms. The hydraulic cylinders are interconnected by cross conduits in such a manner that an upper cylinder chamber of one hydraulic cylinder is communicated with a lower cylinder chamber of the other. The cross conduits are respectively provided with orifices or restrictions and further provided, at locations between the upper cylinder chambers and the restrictions, with spring type mechanical accumulators for pressurizing the hydraulic fluid in the conduits and the cylinders, respectively.
In the prior art device, the restrictions are installed in the cross conduits to restrict flow of hydraulic fluid therethrough during both rolling and bouncing. Accordingly, the prior art device provides a damping force even during bouncing, causing a stiff or rough riding feel and therefore a deteriorated or impaired riding comfort of the vehicle.